1. Field of the Invention
This invention relates to a control apparatus of an internal combustion engine (hereinafter engine) capable of controlling an air-fuel ratio and/or an ignition timing of a mixture to be supplied to the engine.
2. Discussion of Background
FIG. 30 is a explanatory construction diagram showing an embodiment of a conventional control device of engine. As shown in FIG. 30, fuel is sucked and pressurized by the fuel pump 2 from the fuel tank 1, is stabilized of its pulsation by the fuel damper 3, the particle or moisture of which is removed by the fuel filter 4, the pressure of which is made constant by the pressure regulator 5, and is supplied to the fuel injection valve 6.
A numeral 7 signifies a cold start valve for injecting fuel to improve starting of the engine in a cold place.
Furthermore, air which passes through the air cleaner 8, is measured of its quantity, by the air-flow meter 9, is regulated of its flow quantity by the throttle valve 10, passes through the intake manifold 11, is mixed with fuel (air-fuel mixture) by the fuel injection valve 6, and is transported to the cylinder 12.
This mixture is compressed in the cylinder 12, and ignited by the plug 13 at a pertinent timing. Exhaust gas is discharged to the air through the manifold 14 and a purifier, not shown. A numeral 40 signifies an exhaust gas sensor which detects exhaust gas element concentration, (for instance oxygen concentration).
A numeral 15 signifies a water temperature sensor which detects cooling water temperature, 16, a crank angle sensor incorporated in a distributor for detecting rotation angle of a crank shaft of an engine, 17, an ignition device, and 18, a control device which controls air-fuel ratio of a mixture and ignition timing to be supplied to an engine.
The crank angle sensor 16 outputs a reference position signal at every reference position of crank angle (180.degree. CA for four cylinder engine, and 120.degree. CA for six cylinder engine), and outputs a unit angle pulse at every unit angle (for instance every 2.degree. CA). The current crank angle is known, in the control device 18, by counting the number of the unit angle pulses after the reference position pulse is inputted.
The control device 18 is composed of a microcomputer, consisted of a CPU (central processing unit), a RAM (random access memory), a ROM (read only memory), I/O interface and so on. The control device 18 receives a intake air quantity signal Xl from the above mentioned air flow mater 9, water temperature signal X2 from the water temperature sensor 15, a crank angle signal X3 given by the crank angle sensor 16, an exhaust gas signal X10 from the exhaust gas sensor 40, and a battery voltage signal, not shown, or a signal from a throttle-fully-closed-switch and so on, performs calculation in accordance with these signals, of fuel injection quantity to be supplied to the engine, or valve opening time of the fuel injection valve 6, and outputs an injection signal X5.
By this injection signal X5, the fuel injection valve 6 is operated, and fuel of a predetermined quantity is supplied to the engine.
The calculation of the fuel injection quantity (fuel injection time) T.sub.1 in the above control device 18, is performed, for instance by the following equation. EQU T.sub.i =T.sub.p .times.(1+F.sub.t +KMR/100).times..beta.+T.sub.s (1)
In the above equation (1), T.sub.p is a basic injection quantity (basic valve opening time). For instance, assuming that an intake air quantity per one rotation is Q, an engine speed is Ne, and K is a constant, T.sub.p is obtained by the following equation. EQU T.sub.p =K.multidot.Q / N.sub.e
F.sub.t is a correction coefficient which corresponds to the cooling water temperature of the engine, which for instance, becomes a larger value when the cooling water temperature becomes lower.
KMR is a correction coefficient at heavy load time. KMR is read by looking up beforehand a data table in which KMR is described as a value which corresponds with, for instance, a basic fuel injection quantity T.sub.p and the engine speed N.sub.e.
T.sub.s is a correction coefficient by a battery voltage. T.sub.s is a coefficient for correcting a variation of an electric voltage which drives the fuel injection valve 6. For instance, assuming that V.sub.B is a battery voltage, and a and b are constants, T.sub.s is obtained by t.sub.s =a+b (14-V.sub.B). Therefore, the lower the battery voltage, the larger the value of T.sub.s.
.beta. is a correction coefficient which corresponds with exhaust signal X10 from the exhaust gas sensor 40. By using .beta., the air-fuel ratio of the mixture can be controlled by a feed back control, to a value near to a predetermined air-fuel ratio, for instance, a theoretical air-fuel ratio 14.8.
However, when the feed back control by the exhaust signal X10 is carried out, the air-fuel ratio is always controlled to a constant value, the above correction by the cooling water temperature or by high load time becomes meaningless.
Therefore, the feed back control by the exhaust air signal X10 is performed only when a correction
coefficient for water temperature F.sub.t and the correction coefficient for heavy load time KMR is 0.
On the other hand, as an ignition timing control system of an engine, for instance, a system is described in Japanese Unexamined Patent Publication No. 59061/1982.
In this electronic ignition timing control system, for instance, an optimum ignition advance angle value which corresponds with an engine speed N.sub.e and a basic fuel injection quantity T.sub.p, is memorized beforehand in data table. The value of the ignition timing which corresponds to the current engine speed and a basic fuel injection quantity is read out by looking up the table. The ignition signal X6 is outputted to the ignition device 17 so that the ignition timing is controlled to the value, and drives the ignition plug 13.
Since the conventional control device of engine is composed as above, the correction of the fuel injection quantity at heavy load time is determined by the basic injection quantity and the engine speed, or by the intake air quantity and the engine speed. The correction is made by an open loop control. Therefore, the torque of the engine is not necessarily a maximum output torque.
Furthermore, the lowering of the output torque may be generated since the initially set air-fuel ratio and the ignition timing are deviated from the optimam values by the variation and the timewise change of the air flow meter 9, or the fuel injection valve 6, or the engine itself.
In case of an engine having a plurality of cylinders, since output of which cylinder varies each other, the smoothness and silence in the rotation of the engine may be deteriorated.